Method for extending the range of a superconducting-magnetoresistive composite magnetic sensor and measuring device

Abstract

The application discloses a range extension method and a measuring device of a superconducting-magnetic resistance composite magnetic sensor. The application comprises the following steps: acquiring the output voltage of the superconducting-magnetic resistance composite magnetic sensor; when the output voltage is a saturated output voltage V r , generating a compensation magnetic field with a size of B r / 2 and consistent with the saturated magnetic field direction to the superconducting-magnetic resistance composite magnetic sensor, so that the superconducting-magnetic resistance composite magnetic sensor enters the saturated area in the pulse rising edge of the pulse excitation, changes to the intermediate value position of the linear area in the pulse falling edge of the pulse excitation, and calculates the detection output voltage V t according to the final output voltage V x , the pulse excitation frequency n and V r =n×V t +V x . The application can solve the problem of limited range of the superconducting-magnetic resistance composite magnetic sensor, realizes the range extension of the superconducting-magnetic resistance composite magnetic sensor under the premise of simple structure and small size, and realizes the compatibility of high resolution and wide range.

Description

Technical Field

[0001] This invention belongs to the field of weak magnetic field signal detection technology, specifically relating to a method and measuring device for extending the range of a superconducting-magnetoresistive composite magnetic sensor. Background Technology

[0002] Weak magnetic field detection is widely used in geological exploration, biomedicine, target detection, and geomagnetic navigation. Some applications, such as magnetoencephalography (MEG), require magnetic field resolution on the order of fT. Among traditional weak magnetic field sensors, the superconducting quantum interference magnetometer (SQUID), which achieves fT-level magnetic field measurement accuracy, suffers from problems such as large size and demanding shielding environments. Superconducting / magnetoresistive composite sensors can also achieve fT-level detection accuracy and offer advantages such as small size, high stability, and low power consumption, showing great potential for development into miniaturized, high-performance magnetic sensors. A superconducting-magnetoresistive composite magnetic sensor is a magnetic sensor composed of a magnetoresistive sensing unit and a closed loop of superconducting material. The superconducting loop contains one or more narrow regions (narrow areas), and the magnetoresistive sensor is located below these narrow regions and separated by an insulating layer. Below the superconducting critical temperature, when the detected magnetic field passes perpendicularly through a superconducting ring, a shielding current is generated within the ring due to the Meissner effect. When this shielding current passes through a narrow region, its density increases rapidly due to the narrowness of the region, simultaneously generating a locally enhanced magnetic field near the top and bottom of this narrow region. Theoretically, this can achieve magnetic field amplification of over 1000 times, significantly improving the resolution of TMR magnetic sensors. However, high-resolution superconducting / magnetoresistive composite magnetic sensors typically have a low saturation magnetic field, resulting in a very limited measurement range, usually only on the order of μT, far smaller than the magnetic field values ​​required for some applications, such as the Earth's magnetic field which can reach 100,000 nT. Currently, there is no solution that combines high resolution with a wide measurement range for superconducting / magnetoresistive composite magnetic sensors. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and measuring device for extending the range of a superconducting-magnetoresistive composite magnetic sensor, which addresses the above-mentioned problems in the prior art. The present invention can solve the problem of the limited range of the superconducting-magnetoresistive composite magnetic sensor, and can extend the range of the superconducting-magnetoresistive composite magnetic sensor while satisfying the requirements of simple structure and small size, thereby achieving high resolution and wide range compatibility.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for extending the range of a superconducting-magnetoresistive composite magnetic sensor, comprising:

[0006] S101, acquire the output voltage of the superconducting-magnetorresistive composite magnetic sensor in the measured magnetic field x, and measure the output voltage as it increases until it reaches the saturation output voltage V. rAt that time, a pulse excitation is applied to the compensation coil of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field causes the superconducting-magnetoresistive composite magnetic sensor to first enter the saturation region at the rising edge of the pulse excitation, and then change to the midpoint of the linear region at the falling edge of the pulse excitation, with an expansion magnitude of B. r The range is 2 / 2, where B r The magnitude of the saturation magnetic field; and the value of the output voltage is less than the saturation output voltage V. r Output voltage V t If no further increases are observed, proceed to step S102;

[0007] S102, according to V x =n×V r +V t The detection output voltage V corresponding to the measured magnetic field x is calculated. x Where n is the output voltage V. t The number of times the pulse excitation was applied previously.

[0008] Optionally, in step S101, the period of the pulse excitation is greater than 0 and less than a preset threshold close to 0.

[0009] Optionally, in step S102, the detection output voltage V corresponding to the measured magnetic field x is calculated. x This also includes detecting the output voltage V based on the query. x The relationship curve between magnetic fields is used to obtain the magnitude B of the magnetic field corresponding to the measured magnetic field x. x .

[0010] Optionally, before step S101, the saturation output voltage V of the superconducting-magnetoresistive composite magnetic sensor is determined. r And the magnitude of the saturation magnetic field B r .

[0011] Optionally, the determination of the saturated output voltage V r And the magnitude of the saturation magnetic field B r include:

[0012] S201, Apply vertical magnetic fields of different magnitudes to the superconducting-magnetoresistive composite magnetic sensor to obtain the magnetic field-output voltage curves of the superconducting-magnetoresistive composite magnetic sensor under different vertical magnetic fields;

[0013] S202, based on the saturation region of the superconducting-magnetoresistive composite magnetic sensor according to the magnetic field-output voltage curve, determine the magnitude of the saturation magnetic field B based on the saturation region. r and saturated output voltage V r .

[0014] Furthermore, the present invention also provides a measuring device for applying the range extension method of the superconducting-magnetoresistive composite magnetic sensor, comprising a superconducting-magnetoresistive composite magnetic sensor, a comparator, an AC current source, a pulse counter, a multiplier, and an adder. The superconducting-magnetoresistive composite magnetic sensor includes a magnetoresistive sensing element and a compensation coil, wherein: the comparator is used to acquire the output voltage of the superconducting-magnetoresistive composite magnetic sensor in the measured magnetic field x, and each time the output voltage increases to reach a preset saturation output voltage V... r At that time, a control signal is generated to the pulse counter to control the AC current source to apply a pulse excitation to the compensation coil of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field causes the superconducting-magnetoresistive composite magnetic sensor to first enter the saturation region at the rising edge of the pulse excitation, and then change to the midpoint of the linear region at the falling edge of the pulse excitation, with an expansion magnitude of B. r The range is 2 / 2, where B r The magnitude of the saturated magnetic field; the pulse counter is connected to the output terminal of the AC current source to detect and obtain the output voltage V. t The number of times the pulse excitation was previously applied, n; the input terminals of the multiplier are respectively connected to the saturation output voltage V. r The outputs of the comparator and pulse counter are connected to the saturated output voltage V. r / 2. The output voltage V is obtained from the output of the comparator and pulse counter. t Multiply the number of pulse excitations applied previously, n, to obtain the cumulative voltage n×V. r The input terminals of the adder are connected to the output terminals of the multiplier and the magnetoresistive sensing element, respectively, to accumulate the voltage n×V output by the multiplier. r The output voltage V of the magnetoresistive sensing element t Summing yields the detection output voltage V corresponding to the measured magnetic field x. x .

[0015] Optionally, the AC current source outputs a negative pulse waveform of pulse excitation when the comparator outputs -1, outputs a positive pulse waveform of pulse excitation when the comparator outputs 1, and does not output a pulse waveform when the comparator outputs 0.

[0016] Optionally, the superconducting-magnetoresistive composite magnetic sensor further includes a superconducting flux focusing amplifier, the compensation coil is located inside or outside the superconducting flux focusing amplifier, and the sensing element is located on one side of a narrow region on the superconducting flux focusing amplifier.

[0017] Optionally, the compensation coil is a superconducting coil.

[0018] Optionally, the output of the adder is also connected to a preamplifier circuit and a signal processing circuit.

[0019] Compared with the prior art, the present invention has the following main advantages: The present invention includes obtaining the output voltage of a superconducting-magnetoresistive composite magnetic sensor in the measured magnetic field x, wherein each time the output voltage increases to reach the saturation output voltage V r At that time, a pulse excitation is applied to the compensation coil of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field causes the superconducting-magnetoresistive composite magnetic sensor to first enter the saturation region at the rising edge of the pulse excitation, and then change to the midpoint of the linear region at the falling edge of the pulse excitation, with an expansion magnitude of B. r The range is 2 / 2, and the output voltage value is less than the saturation output voltage V. r Output voltage V t And when it no longer increases, according to V x =n×V r +V t The detection output voltage V corresponding to the measured magnetic field x is calculated. x This invention utilizes a compensating magnetic field to alter the operating position of a superconducting-magnetoresistive composite magnetic sensor. This effectively extends the magnetic field measurement range of the superconducting / magnetoresistive composite magnetic sensor while maintaining device miniaturization, thus solving the problem of limited range in superconducting-magnetoresistive composite magnetic sensors. It achieves range extension (n×V) of the superconducting-magnetoresistive composite magnetic sensor while maintaining a simple structure and small size. r This is the extended range portion, thus achieving high resolution and wide range compatibility to simultaneously realize high-precision, wide-range magnetic field measurement. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the principle of the method in an embodiment of the present invention.

[0021] Figure 2 This is the magnetic field-output voltage curve in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the magnetic field-output voltage curve after the range is extended and the voltage returns to the middle position of the linear region in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the magnetic field-output voltage curve of the compensation magnetic field in an embodiment of the present invention.

[0024] Figure 5 This is a comparative diagram showing the measurement range before and after expansion in an embodiment of the present invention.

[0025] Figure 6This is a schematic diagram of the measuring device in an embodiment of the present invention. Detailed Implementation

[0026] like Figure 1 As shown, the range extension method for the superconducting-magnetoresistive composite magnetic sensor in this embodiment includes:

[0027] S101, acquire the output voltage of the superconducting-magnetorresistive composite magnetic sensor in the measured magnetic field x, and measure the output voltage as it increases until it reaches the saturation output voltage V. r At that time, a pulse excitation is applied to the compensation coil of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field causes the superconducting-magnetoresistive composite magnetic sensor to first enter the saturation region at the rising edge of the pulse excitation, and then change to the midpoint of the linear region at the falling edge of the pulse excitation, with an expansion magnitude of B. r The range is 2 / 2, where B r The magnitude of the saturation magnetic field; and the value of the output voltage is less than the saturation output voltage V. r Output voltage V t If no further increases are observed, proceed to step S102;

[0028] S102, according to V x =n×V r +V t The detection output voltage V corresponding to the measured magnetic field x is calculated. x Where n is the output voltage V. t The number of times the pulse excitation was applied previously.

[0029] In this embodiment, the period of the pulse excitation in step S101 is greater than 0 and less than a preset threshold close to 0, so that the pulse time for forming the compensation magnetic field is as short as possible, thereby reducing the loss of magnetic field information and achieving a rapid response to the measured magnetic field.

[0030] In this embodiment, the detection output voltage V corresponding to the measured magnetic field x is calculated in step S102. x This also includes detecting the output voltage V based on the query. x The relationship curve between magnetic fields is used to obtain the magnitude B of the magnetic field corresponding to the measured magnetic field x. x The output voltage V is detected. x The relationship curve between magnetic fields can be obtained by pre-calibrating with magnetic fields of different fixed magnitudes.

[0031] In this embodiment, before step S101, the saturation output voltage V of the superconducting-magnetoresistive composite magnetic sensor is determined. r And the magnitude of the saturation magnetic field B rSpecifically, in this embodiment, the saturated output voltage V is determined. r And the magnitude of the saturation magnetic field B r include:

[0032] S201, Apply vertical magnetic fields of different magnitudes to the superconducting-magnetoresistive composite magnetic sensor to obtain the magnetic field-output voltage curves of the superconducting-magnetoresistive composite magnetic sensor under different vertical magnetic fields;

[0033] S202, based on the saturation region of the superconducting-magnetoresistive composite magnetic sensor according to the magnetic field-output voltage curve, determine the magnitude of the saturation magnetic field B based on the saturation region. r and saturated output voltage V r .like Figure 3 In the magnetic field-output voltage curve shown, the horizontal axis B represents the magnetic field magnitude, and the vertical axis V represents the output voltage. r The area shown is the saturated magnetic field, and position A is the maximum saturated magnetic field. The voltage corresponding to position A is the saturated output voltage V. r .

[0034] Figure 3 This is a schematic diagram of the magnetic field-output voltage curve after the range is extended and the voltage returns to the middle position of the linear region in step S101 of this embodiment. See [link / reference] Figure 3 Whenever the output voltage increases to position A, a pulse excitation is applied to the compensation coil of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. Compensating magnetic field whose direction is consistent with the saturation magnetic field, such as Figure 3 As shown, the superconducting-magnetoresistive composite magnetic sensor first enters the saturation region (reaching position C) at the rising edge of the pulse excitation pulse, and then changes to the midpoint of the linear region (reaching position D) at the falling edge of the pulse excitation pulse, with an expansion size of B. r / 2 range, Figure 4 This is a schematic diagram of the compensation magnetic field in an embodiment of the present invention. The compensation magnetic field can make the output voltage... Figure 4 The magnetic field-output voltage curve shown goes from position A through position C to position D, thus expanding to a size of B. r / 2 range.

[0035] Figure 5 This is a comparative diagram of the range extension in this embodiment. (a) shows the magnetic field-output voltage curve before range extension, while (b) shows the magnetic field-output voltage curve after range extension. The output of the superconducting-magnetoresistive composite magnetic sensor when it reaches positive saturation is V. r The range before expansion is B. r For the positive magnetic field B being measured t ,like Figure 5As shown in (a), the output of the extended superconducting-magnetoresistive composite magnetic sensor is V. r ;like Figure 5 As shown in (b), after expansion, the sensor output voltage reaches V each time. r At that time, the range of the superconducting-magnetoresistive composite magnetic sensor is extended by B. r / 2, for the measured magnetic field B t The final output voltage of the superconducting-magnetoresistive composite magnetic sensor is V. t During the test, the output voltage reached V four times. r That is, the range has been extended by 4×B r / 2, so the actual magnetic field should be V t The corresponding magnetic field is increased by 4×B r / 2.

[0036] like Figure 6 As shown, the measuring device for applying the aforementioned range extension method of the superconducting-magnetoresistive composite magnetic sensor in this embodiment includes a superconducting-magnetoresistive composite magnetic sensor 1, a comparator 2, an AC current source 3, a pulse counter 4, a multiplier 5, and an adder 6. The superconducting-magnetoresistive composite magnetic sensor 1 includes a magnetoresistive sensing element 11 and a compensation coil 13. The comparator 2 is used to acquire the output voltage of the superconducting-magnetoresistive composite magnetic sensor in the measured magnetic field x. Whenever the output voltage increases to reach a preset saturation output voltage V... r At that time, a control signal is generated to the pulse counter 4 to control the AC current source 3 to apply a pulse excitation to the compensation coil 13 of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field causes the superconducting-magnetoresistive composite magnetic sensor to first enter the saturation region at the rising edge of the pulse excitation, and then change to the midpoint of the linear region at the falling edge of the pulse excitation, with an expansion magnitude of B. r The range is 2 / 2, where B r The magnitude of the saturated magnetic field; the pulse counter 4 is connected to the output terminal of the AC current source 3 to detect and obtain the output voltage V. t The number of times the pulse excitation was previously applied, n; the input terminals of the multiplier 5 are respectively connected to the saturation output voltage V. r The outputs of comparator 2 and pulse counter 4 are connected to each other to convert the saturated output voltage V. r / 2. The output voltage V is obtained from the outputs of comparator 2 and pulse counter 4. t Multiply the number of pulse excitations applied previously, n, to obtain the cumulative voltage n×V. r The input terminal of the adder 6 is connected to the output terminal of the multiplier 5 and the output terminal of the magnetoresistive sensing element 11 respectively, so as to accumulate the voltage n×V output by the multiplier 5. rThe output voltage V of the magnetoresistive sensing element 11 t Summing yields the detection output voltage V corresponding to the measured magnetic field x. x .

[0037] In this embodiment, the comparator only outputs three voltage levels: -1, 0, and 1. The AC current source 3 outputs a negative pulse waveform when comparator 2 outputs -1, a positive pulse waveform when comparator 2 outputs 1, and no pulse waveform when comparator 2 outputs 0. When the sensor's output voltage reaches positive saturation V for the nth time... r At position, the output voltage V r Level output 1, count value (obtain output voltage V) t The number of times pulse excitation has been applied previously is n, and the multiplier input is V. r ×1×n=n×Vr means that the sensor range has been extended in the positive direction by n×(B) r / 2); When the sensor's output voltage reaches negative positive saturation -V for the nth time. r At position, the voltage output is -V r The output level is -1, the count value is n, and the multiplier input is -V. r ×-1×n=n×V r This means that the sensor's range has been extended by n×(B) in both the positive and negative directions. r / 2).

[0038] In this embodiment, the superconducting-magnetoresistive composite magnetic sensor 1 further includes a superconducting flux focusing amplifier 12. The compensation coil 13 is located inside or outside the superconducting flux focusing amplifier 12, and the sensing element 11 is located on one side of the narrow region 121 (sensitive region) on the superconducting flux focusing amplifier 12. In this embodiment, the compensation coil 13 is a superconducting coil, which can result in lower power consumption. In this embodiment, the output terminal of the adder 6 is also connected to a pre-amplifier circuit and a signal processing circuit, resulting in higher integration and facilitating the application of the measurement device in this embodiment.

[0039] In summary, this embodiment utilizes a compensating magnetic field to alter the operating position of the superconducting-magnetoresistive composite magnetic sensor. This effectively extends the magnetic field measurement range of the superconducting / magnetoresistive composite magnetic sensor while maintaining device miniaturization. It solves the problem of the limited range of the superconducting-magnetoresistive composite magnetic sensor and achieves range extension (n×V) while maintaining a simple structure and small size. r This is the extended range portion, thus achieving high resolution and wide range compatibility to simultaneously realize high-precision, wide-range magnetic field measurement.

[0040] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for extending the range of a superconducting-magnetoresistive composite magnetic sensor, characterized in that, include: S101, acquire the output voltage of the superconducting-magnetorresistive composite magnetic sensor in the measured magnetic field x, and measure the output voltage as it increases until it reaches the saturation output voltage V. r At that time, a pulse excitation is applied to the compensation coil of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field ensures that the superconducting-magnetoresistive composite magnetic sensor first remains in the saturation region at the rising edge of the pulse excitation, and then changes to the midpoint of the linear region at the falling edge of the pulse excitation, expanding to a magnitude of B. r The range is 2 / 2, where B r The magnitude of the saturation magnetic field; and the value of the output voltage is less than the saturation output voltage V. r Output voltage V t If no further increases are observed, proceed to step S102; S102, according to V x =n×V r +V t The detection output voltage V corresponding to the measured magnetic field x is calculated. x Where n is the output voltage V. t The number of times the pulse excitation was applied previously.

2. The method for extending the range of the superconducting-magnetoresistive composite magnetic sensor according to claim 1, characterized in that, In step S101, the period of the pulse excitation is greater than 0 and less than a preset threshold close to 0.

3. The method for extending the range of the superconducting-magnetoresistive composite magnetic sensor according to claim 2, characterized in that, In step S102, the detection output voltage V corresponding to the measured magnetic field x is calculated. x This also includes detecting the output voltage V based on the query. x The relationship curve between magnetic fields is used to obtain the magnitude B of the magnetic field corresponding to the measured magnetic field x. x .

4. The method for extending the range of the superconducting-magnetoresistive composite magnetic sensor according to claim 1, characterized in that, Before step S101, the saturation output voltage V of the superconducting-magnetoresistive composite magnetic sensor is determined. r And the magnitude of the saturation magnetic field B r .

5. The method for extending the range of the superconducting-magnetoresistive composite magnetic sensor according to claim 4, characterized in that, The determination of saturated output voltage V r And the magnitude of the saturation magnetic field B r include: S201, Apply vertical magnetic fields of different magnitudes to the superconducting-magnetoresistive composite magnetic sensor to obtain the magnetic field-output voltage curves of the superconducting-magnetoresistive composite magnetic sensor under different vertical magnetic fields; S202, based on the saturation region of the superconducting-magnetoresistive composite magnetic sensor according to the magnetic field-output voltage curve, determine the magnitude of the saturation magnetic field B based on the saturation region. r and saturated output voltage V r .

6. A measuring device for applying the range extension method of the superconducting-magnetoresistive composite magnetic sensor according to any one of claims 1 to 5, characterized in that, The system includes a superconducting-magnetoresistive composite magnetic sensor (1), a comparator (2), an AC current source (3), a pulse counter (4), a multiplier (5), and an adder (6). The superconducting-magnetoresistive composite magnetic sensor (1) includes a magnetoresistive sensing element (11) and a compensation coil (13). The comparator (2) is used to acquire the output voltage of the superconducting-magnetoresistive composite magnetic sensor in the measured magnetic field x. Whenever the output voltage increases to reach a preset saturation output voltage V, the comparator is used to acquire the output voltage of the superconducting-magnetoresistive composite magnetic sensor. r At that time, a control signal is generated to the pulse counter (4) to control the AC current source (3) to apply a pulse excitation to the compensation coil (13) of the superconducting-magnetoresistive composite magnetic sensor to form a pulse of magnitude B. r / 2. A compensating magnetic field with the same direction as the saturation magnetic field ensures that the superconducting-magnetoresistive composite magnetic sensor first remains in the saturation region at the rising edge of the pulse excitation, and then changes to the midpoint of the linear region at the falling edge of the pulse excitation, expanding to a magnitude of B. r The range is 2 / 2, where B r The magnitude of the saturated magnetic field; the pulse counter (4) is connected to the output terminal of the AC current source (3) to detect and obtain the output voltage V. t The number of times the pulse excitation was previously applied, n; the input terminals of the multiplier (5) are respectively connected to the saturation output voltage V. r The output terminals of the comparator (2) and the pulse counter (4) are connected to each other to convert the saturated output voltage V. r / 2. The output voltage V is obtained from the output of comparator (2) and pulse counter (4). t Multiply the number of pulse excitations applied previously, n, to obtain the cumulative voltage n×V. r The input terminal of the adder (6) is connected to the output terminal of the multiplier (5) and the output terminal of the magnetoresistive sensing element (11) respectively, so as to accumulate the voltage n×V output by the multiplier (5). r The output voltage V of the magnetoresistive sensing element (11) t Summing yields the detection output voltage V corresponding to the measured magnetic field x. x .

7. The measuring device according to claim 6, characterized in that, The AC current source (3) outputs a negative pulse waveform of pulse excitation when the comparator (2) outputs -1, outputs a positive pulse waveform of pulse excitation when the comparator (2) outputs 1, and does not output a pulse waveform when the comparator (2) outputs 0.

8. The measuring device according to claim 7, characterized in that, The superconducting-magnetoresistive composite magnetic sensor (1) also includes a superconducting flux focusing amplifier (12), the compensation coil (13) is located inside or outside the superconducting flux focusing amplifier (12), and the sensitive element (11) is located on one side of the narrow region (121) on the superconducting flux focusing amplifier (12).

9. The measuring device according to claim 8, characterized in that, The compensation coil (13) is a superconducting coil.

10. The measuring device according to claim 9, characterized in that, The output of the adder (6) is also connected to a preamplifier circuit and a signal processing circuit.

Images